Pushing devices for mine conveyors



April 9, 1963 w. H. BARRETT 3,084,920

PUSHING DEVICES FOR MINE CONVEYORS Filed Feb. 27, 1961 2 Sheets-Sheet 2 32 34 37 g fi E [a Y Q FIG. 8.

INVENTOR we'ui 8MKif7 ATTQRNEYs United States Patent Ofiiice 3,084,929 Patented Apr. 9, 1963 3,084,920 PUSHING DEVECES FOR MINE CONVEYORS Wesley H. Barrett, Qheltcnham, England, assignor t Dowty Mining Equipment Limited, Ashchurch, England, a British company Filed Feb. 27, 1961, tier. No. 92,076 Claims priority, application Great Britain Mar. 2, 1960 8 Claims. (Cl. 262-1) This invention relates to pushing devices for a conveyor at the face of a mine where coal is stripped by traversing a plough along the face in front of a flexible conveyor, the pressure on which caused by the pushing devices is used to hold the plough against the coal face. The pushing device is broadly of the known kind comprising a push-pull jack mounted on a strut which may either be a simple strut arranged to be jammed between the floor and roof of the mine or a roof support unit arranged to be extended between the floor and roof, the jack being connected to the conveyor for advancing same when the strut is fixed and for advancing the strut by pulling on the conveyor when the strut is free. Such pushing device will hereinafter be referred to as a pushing device for the purpose specified.

In using such a pushing device on a plough face, it is important not to advance the strut so close to the conveyor that the jack is unable to contract through the distance by which the adjacent section of the conveyor is pushed back when the plough traverses in front of the pushing device. The required limit to contraction of the jack during the advance of the strut is automatically provided, in accordance with the invention, by a lostmotion mounting of the jack between the strut and the conveyor which provides an extent of free longitudinal movement during hydraulic operation of the jack which is not less than the elfective depth of the plough through which the conveyor sections are pushed back.

The invention is illustrated in the drawings accompanying this specification, of which:

FIGURE 1 is a plan view of an abutment strut formed as a roof support unit having a push-pull jack with a lost-motion mounting;

FIGURE 2 is a side elevation of the unit shown connected to a conveyor;

FIGURE 3 is a part sectional view of the jack mounting on the line IIIIII of FIGURE 1;

FIGURES 4 to 8 are sequence diagrams showing the operation of the push-pull jack;

FIGURE 9 is a detail view in plan and partly in section showing one of the linked connections between the yoke on which the push-pull jack is mounted and one of the floor bars of the roof support unit.

The roof support unit comprises two extensible and contractable parallel frames 18 each having a floor bar 19, two telescopic props 21, mounted in sockets 22, 23 on the floor bar, and a cantilever roof bar 24 carried by the heads of the props 21. The frames 18 are connected by two pairs of transverse spring steel strips 25 which are secured at their ends to raised front portions of the floor bars 19, and by a transverse spring steel strip 26 which is held at each end between the head of the rearmost prop 21 and the roof bar 24.

A yoke 27 extends transversely between the floor bars 19 beneath the front steel strips 25, and it is connected by links 28 to pins 29 which are fixed on the inner sides of the floor bars 19. FIGURE 9 shows the connection at one side of the yoke provided by a link 28 which is pivoted at its forward end on a pin 30 fixed in the yoke 27, and which is pivoted at its rearward end on the pin 29. The connection at the other side of the yoke is similar. There is sufficient play in the pivoted connections of the links 28 on the pins 29 and 30 to enable the yoke 27 to move a small distance and away from engagement with abutments 31 which are fixed on the inner sides of the floor bars 19. This end play is merely to enable a forwardly acting load on the yoke 27 to be taken in tension by the links 28 while a rearwardly acting load on the yoke 27 is sustained directly by the abutments 31 on the floor bars 19. The end play referred to is so small that it can be disregarded in the operation sequence hereinafter described. Two screws 32 are fixed on a vertical axis at the centre of the yoke 27 to locate a double-acting push-pull hydraulic jack 33. The jack 33 comprises a cylinder 34 having plates 35 fixed on its upper and lower sides, while longitudinal slots 36 in the plates 35 receive the inner ends of the screws 32 to form a pin and slot lost-motion mounting for the cylinder 34. The jack 33 has a piston rod 37 extending forwardly into pivotal engagement at 38 'with the side of a flexible conveyor 39. The opposite ends of the slots 36 form stops which permit longitudinal movement of the cylinder 34 in the yoke 27 through a distance which is not less than the effective depth of the plough through which the conveyor 39 is pushed rearwardly upon traverse of the coal plough (not shown) on the face side of the conveyor. The jack 33 can pivot about the screws 32 to allow for the pivotal connection 38 with the conveyor 39 being off-centre with respect to the roof support unit.

It is to be understood that a number of roof support units of the kind described will in use be spaced side by side along the coal face with their jacks 33 acting in thrust against the conveyor 39 to maintain cutting pressure of the plough on the coal face.

The sequence of operations will now be described with reference to FIGURES 4 to 8. The jack 33 is shown in FIGURE 4 with the piston 41 displaced from the rear end of the cylinder 34 through a distance which is at least equal to the depth of the plough. During coal cutting fluid pressure acts through the rear end of the cylinder 34 on the full area of the piston 41 and the piston 41 can yield in the cylinder 34 as the plough passes without bottoming on the rear of the cylinder 34. As the coal face is advanced by successive traverses of the coal plough, the piston 41 advances towards the front end of the cylinder 34, as shown in FIGURE 5, and at or before this stage is reached it is necessary to advance the roof support unit bodily. The full area of the piston 41 is therefore relieved of fluid pressure, and fluid pressure is applied through the front end of the cylinder 34 to the annular area of the piston 41, causing the cylinder 34 first to travel forward until the screws 32 in the yoke 27 engage the rear ends of the slots 36 as shown in FIG- URE 6. Continued application of fluid pressure then advances the roof support unit until the piston 41 bottoms on the rear end of the cylinder 34, as shown in FIGURE 7. The roof support unit is then reset between the floor and roof of the mine after which fluid pressure on the piston 41 is reversed. This causes the cylinder 34 to travel rearwardly to the extent permitted by the engagement of the screws 32 in the slots 36 until the condition of FIGURE 8 is reached at which the screws 32 engage the forward ends of the slots 36.

The piston 41 then lies at a distance from the rear end of the cylinder 34 which enables the conveyor 39 to yield as the plough passes in front of the roof support unit without causing the piston 41 to bottom on the rear end of the cylinder 34.

It is thus seen that the lost-motion device formed by the screws 32 and slots 36 automatically provides the required amount of yielding travel of the piston 41 in the cylinder 34 when the roof support unit is fully advanced.

It is possible to advance each roof support unit in turn without interrupting the operation of the coal plough, as the necessary thrust on the conveyor 39 can be substantially maintained by the jacks 34 of the roof support units adjacent the one unit being advanced.

I claim as my invention:

1. A pushing device for the purpose specified comprising a strut adapted to be fixed between the floor arni roof of a mine, a double-acting jack having piston and cylinder members one of which is adapted for connection with a conveyor, and a mounting by which the other jack memher is connected to the strut, said mounting comprising a lost-motion device arranged to provide between the limits of the lost-motion device free longitudinal movement of said other jack member with respect to the strut, said lost-motion device including two slots formed longitudinally on opposite sides of the jack cylinder, and two pins disposed on a vertical axis in longitudinally fixed relationship to the strut, said pins engaging the respective slots to form pivots about which the jack cylinder can turn as well as on which the jack cylinder can slide.

2. A pushing device for the purpose specified compris ing extensible and contractable strut means adapted for interposition between the floor and the roof of a mine, a double-acting jack having telescopic piston and cylinder members, one of said telescopic members extending from the strut means and being adapted at its outer end for connection with a conveyor, and a lost-motion mounting by which the other of said telescopic members is located on the strut means, said lost-motion mounting including co-operable stop means disposed on the strut and on said other telescopic member in positions which are spaced longitudinally of the latter to determine the limits of free longitudinal movement of said other telescopic member with respect to the strut means.

3. A pushing device according to claim 2, wherein the lost-motion device includes guide means comprising two slots formed longitudinally on opposite sides of the jack cylinder, and wherein the co-operable stop means is provided respectively by the ends of the slots and by two pins disposed on a vertical axis in longitudinally fixed relationship to the strut, said pins coaXially engaging the respective slots to form pivots about which the jack cylinder can turn as well as on which the jack cylinder can slide.

4. In combination, a strut capable of fixture between two spaced surfaces, a double-acting piston jack, and means for mounting the jack on the strut, said mounting means including lost-motion means connecting the jack with the strut for relative displacement therebetween over an elongated path extending longitudinally of the jack and the lost-motion means including terminal stops interengageable at points spaced apart by a distance predetermined in relation to the stroke of the jack piston.

5. The combination according to claim 4 wherein said mounting means includes means on one of the strut and the jack defining a slot forming said path for the specified relative displacement therebetween, and means received in said slot and carried by the other of the strut and the jack, for slidable engagement in the slot, and for engage ment with terminal stops at the ends of the slot.

6. The combination according to claim 5 wherein the jack includes a cylinder for the piston, said cylinder hav ing the slot therein and the terminal stops at the ends of said slot.

7. The combination according to claim 5 wherein the other of said strut and said jack has a pivot pin thereon engaged in the slot for sliding movement therein, and for engagement with the terminal stops at the ends of the slot.

8. In combination, a strut capable of fixture between two spaced parallel surfaces, a double-acting jack having telescopic piston and cylinder members, and means for mounting the jack on the strut, said mounting means including lost-motion means connecting one of the piston and cylinder members with the strut for relative displacement therebetween over an elongated path extending longitudinally of the jack, and said lost-motion means including a stop element carried by one of the strut and the jack member, and terminal stops on the other engageable thereby at points spaced apart by a distance predetermined in relation to the stroke of the piston in the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,910,281 Wilkenloh et al. Oct. 27, 1959 

1. A PUSHING DEVICE FOR THE PURPOSE SPECIFIED COMPRISING A STRUT ADAPTED TO BE FIXED BETWEEN THE FLOOR AND ROOF OF A MINE, A DOUBLE-ACTING JACK HAVING PISTON AND CYLINDER MEMBERS ONE OF WHICH IS ADAPTED FOR CONNECTION WITH A CONVEYOR, AND A MOUNTING BY WHICH THE OTHER JACK MEMBER IS CONNECTED TO THE STRUT, SAID MOUNTING COMPRISING A LOST-MOTION DEVICE ARRANGED TO PROVIDE BETWEEN THE LIMITS OF THE LOST-MOTION DEVICE FREE LONGITUDINAL MOVEMENT OF SAID OTHER JACK MEMBER WITH RESPECT TO THE STRUT, SAID LOST-MOTION DEVICE INCLUDING TWO SLOTS FORMED LONGITUDINALLY ON OPPOSITE SIDES OF THE JACK CYLINDER, AND TWO PINS DISPOSED ON A VERTICAL AXIS IN LONGITUDINALLY FIXED RELATIONSHIP TO THE STRUT, SAID PINS ENGAGING THE RESPECTIVE SLOTS TO FORM PIVOTS ABOUT WHICH THE JACK CYLINDER CAN TURN AS WELL AS ON WHICH THE JACK CYLINDER CAN SLIDE. 